Google and Apple are attracting scrutiny for flying “military-grade spy planes” over major U.S. cities as they race to shore up their rival 3D-mapping services.

Staffers for Sen. Charles Schumer met with Google officials Monday to discuss privacy issues related to the camera-equipped planes. They plan to meet with Apple on Friday.

The senator’s office also plans to reach out to other companies developing similar technologies.

Schumer said in a statement Tuesday that he wanted Apple and Google to clarify their plans and ensure “they understand the significance of our concerns over the potential publication of images captured in people’s backyards and other private settings.”

On Monday, Schumer wrote to the two rival Silicon Valley corporations, accusing them of “an unprecedented invasion of privacy” by using filming technology capable of imaging objects as small as 4 inches.

In his letter, Schumer raised concerns over Apple’s and Google’s reported “digital mapping plans that use military-grade spy planes with enough precision to see through windows, catch detailed images of private backyard activities, and record images as small as 4 inches.”